Hairpin winding electric machine

ABSTRACT

An electric machine includes a stator core defining slots and a winding disposed in the core and having three phases. Each of the phases has at least two parallel paths including hairpins interconnected to form at least two continuous circuits between a terminal and a neutral. The hairpins of each path include: a first type of hairpins (first hairpins) each having first and second legs spaced apart by a span of five slots; a second type of hairpins (second hairpins) each having first and second legs spaced apart by a span of seven slots; and a third type of hairpins (first hairpins) each having first and second legs spaced apart by a span of five or seven slots.

TECHNICAL FIELD

The present disclosure relates to electric machines and morespecifically to electric machines that include hairpin windings.

BACKGROUND

Vehicles such as fully electric vehicles and hybrid-electric vehiclescontain a traction-battery assembly to act as an energy source for thevehicle. The traction battery may include components and systems toassist in managing vehicle performance and operations. The tractionbattery may also include high-voltage components, and an air or liquidthermal-management system to control the temperature of the battery. Thetraction battery is electrically connected to an electric machine thatprovides torque to driven wheels. Electric machines typically include astator and a rotor that cooperate to convert electrical energy intomechanical motion or vice versa.

SUMMARY

According to one embodiment, an electric machine includes a stator coredefining slots having a plurality of radial positions including an innerposition, an outer position, and a pair of middle positions. Adouble-layer winding is disposed in the core and has first and secondparallel paths each including hairpins directly interconnected to eachother to form a continuous circuit between a terminal and a neutralwithout using jumpers. Each of the hairpins includes a first legdisposed in one of the slots, a second leg disposed in another of theslots, a crown connecting between the legs, and at least one inwardlyextending twist joined to one of the legs. For each of the paths, afirst subset of the hairpins (first hairpins) have their first andsecond legs disposed in the inner position and a second subset of thehairpins (second hairpins) have their first and second legs disposed inthe outer position.

According to another embodiment, an electric machine includes a statorcore defining slots and a winding disposed in the core and having threephases. Each of the phases has at least two parallel paths includinghairpins interconnected to form at least two continuous circuits betweena terminal and a neutral. The hairpins of each path include: a firsttype of hairpins (first hairpins) each having first and second legsspaced apart by a span of five slots; a second type of hairpins (secondhairpins) each having first and second legs spaced apart by a span ofseven slots; and a third type of hairpins (first hairpins) each havingfirst and second legs spaced apart by a span of five or seven slots.

According to yet another embodiment, an electric machine includes astator core defining slots having a plurality of radial positions andjumperless windings disposed in the core and arranged in three phaseseach having at least two paths including hairpins interconnected to format least two continuous circuits between a terminal and a neutral. Thehairpins of each path include: a first type of hairpins (first hairpins)each having a first leg, a second leg, a crown connecting between thelegs, an outwardly extending twist joined to the first leg, and aninwardly extending twist joined to the second leg, wherein the legs arespaced apart by a span of five slots and are located in a same first oneof the radial positions; a second type of hairpins (second hairpins)each having a first leg, a second leg, a crown connecting between thelegs, an inwardly extending twist joined to the first leg, and anoutwardly extending twist joined to the second leg, wherein the legs arespaced apart by a span of seven slots and are located in a same secondone of the radial positions; and a third type of hairpins (thirdhairpins) each having a first leg disposed in a third one of the radialpositions, a second leg disposed in a fourth one of the radialpositions, a crown connecting between the legs, a first inwardlyextending twist joined to the first leg, and a second inwardly extendingtwist joined to the second leg, wherein the legs are spaced apart by aspan of five or seven slots. At least one of the slots only has one ofthe phases disposed therein, and at least one of the slots has two ofthe phases disposed therein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an electric machine.

FIG. 2 is a cross-sectional end view of a stator of the electricmachine.

FIG. 3 is a diagrammatical perspective view of a winding of the electricmachine with legs of the hairpins substantially shortened forillustrative purposes.

FIG. 4A is a perspective view of a first type of hairpin.

FIG. 4B is a perspective view of a second type of hairpin.

FIG. 4C is a perspective view of a third type of hairpin.

FIG. 4D is a perspective view of a fourth type of hairpin.

FIG. 4E is a perspective view of a fifth type of hairpin.

FIG. 5 is a magnified view of portion of FIG. 2.

FIG. 6 is a winding diagram of a U phase of the windings looking from aweld side (also known as a twist side) of the stator.

FIG. 7 is a detail view of the U-phase winding diagram showing of ablock of a first path of the U phase.

FIG. 8 is a winding diagram of a V phase of the windings looking fromthe weld side of the stator.

FIG. 9 is a winding diagram of a W phase of the windings looking fromthe weld side of the stator.

DETAILED DESCRIPTION

Embodiments of the present disclosure are described herein. It is to beunderstood, however, that the disclosed embodiments are merely examplesand other embodiments can take various and alternative forms. Thefigures are not necessarily to scale; some features could be exaggeratedor minimized to show details of particular components. Therefore,specific structural and functional details disclosed herein are not tobe interpreted as limiting, but merely as a representative basis forteaching one skilled in the art to variously employ the presentinvention. As those of ordinary skill in the art will understand,various features illustrated and described with reference to any one ofthe figures can be combined with features illustrated in one or moreother figures to produce embodiments that are not explicitly illustratedor described. The combinations of features illustrated providerepresentative embodiments for typical applications. Variouscombinations and modifications of the features consistent with theteachings of this disclosure, however, could be desired for particularapplications or implementations.

Referring to FIG. 1, a hairpin electric machine 20 may be used in avehicle such as a fully electric vehicle or a hybrid-electric vehicle.The electric machine 20 may be referred to as an electric motor, atraction motor, a generator, or the like. The electric machine 20 may bea permanent magnet machine, an induction machine, or the like. In theillustrated embodiment, the electric machine 20 is a three-phasealternating current (AC) machine. The electric machine 20 is capable ofacting as both a motor to propel the vehicle and as a generator such asduring regenerative braking.

The electric machine 20 may be powered by a traction battery of thevehicle. The traction battery may provide a high-voltage direct current(DC) output from one or more battery-cell arrays, sometimes referred toas battery-cell stacks, within the traction battery. The battery-cellarrays may include one or more battery cells that convert storedchemical energy to electrical energy. The cells may include a housing, apositive electrode (cathode), and a negative electrode (anode). Anelectrolyte allows ions to move between the anode and cathode duringdischarge, and then return during recharge. Terminals allow current toflow out of the cells for use by the vehicle.

The traction battery may be electrically connected to one or more powerelectronics modules. The power electronics modules may be electricallyconnected to the electric machines 20 and may provide the ability tobi-directionally transfer electrical energy between the traction batteryand the electric machine 20. For example, a typical traction battery mayprovide a DC voltage while the electric machine 20 may require athree-phase (AC) voltage. The power electronics module may include aninverter that converts the DC voltage to a three-phase AC voltage asrequired by the electric machine 20. In a regenerative mode, the powerelectronics module may convert the three-phase AC voltage from theelectric machine 20 acting as a generator to the DC voltage required bythe traction battery.

Referring to FIGS. 1 and 2, the electric machine 20 includes a housing21 that encloses the stator 22 and the rotor 24. The stator 22 is fixedto the housing 21 and includes a cylindrical core 32 having an innerdiameter 28 that defines a hole 30 and an outer diameter 29. The core 32may be formed from a plurality of stacked laminations. The rotor 24 issupported for rotation within the hole 30. The rotor 24 may includewindings or permanent magnets that interact with windings of the stator22 to generate rotation of the rotor 24 when the electric machine 20 isenergized. The rotor 24 may be supported on a driveshaft 26 that extendsthrough the housing 21. The driveshaft 26 is configured to couple with adrivetrain of the vehicle.

The stator core 32 defines slots 34 circumferentially arranged aroundthe core 32 and extending outward from the inner diameter 28. The slots34 may be equally spaced around the circumference and extend axiallyfrom a first end 36 of the core 32 to a second end 38. In theillustrated embodiment, the core 32 defines forty-eight slots and haseight poles, but the core 32 may include more or fewer slots and/orpoles in other embodiments. For example, the core 32 may defineseventy-two slots and have 12 poles. According to one embodiment, eachslot is 30 electrical degrees. The electric machine 20 may be adouble-layer machine meaning that some of the slots contain more thanone phase. In the illustrated embodiment, half of the slots contain twophases and the other half of the slots include a single phase. This isin contrast to a single-layer machine where each slot only contains asingle phase.

The slots 34 are spaced by a circumferential distance measured betweenthe center lines of two adjacent slots. This distance can be used as aunit of distance (hereinafter “a slot”) for relating and measuring othercomponents of the stator 22. The distance unit “slot” is sometimesreferred to as “slot pitch” or “slot span.”

Referring to FIGS. 2 and 3, the electric machine 20 may include hairpinwindings 40 placed in the slots 34 of the core 32. Hairpin windings arean emerging technology that improves efficiency for electric machinesused in vehicles and other applications. The hairpin windings 40 improveefficiency by providing a greater amount of stator conductors to reduceresistance of the winding 40 without encroaching into space reserved forthe electrical steel and the magnetic flux path.

One challenge with a hairpin winding is matching the electric-machinedesign to the desired torque-speed curve. An essential step in designingan electric machine is selecting the phase turn number so that thetorque-speed curve covers all required operating points. Forconventional stranded windings made of long wires connected in parallel,the desired phase turn number is selected by choosing the number ofturns per coil, the number of parallel paths, the number of poles, thenumber of slots per pole, and the number of layers. While all thesefactors are also available for hairpin windings, the limiting factorsare very different resulting in fewer feasible choices.

For example, while the possible number of poles, slots per pole, andlayers are identical between the two technologies, it is not practicalin a hairpin winding to have as many turns per coil as in a strandedwinding. Each hairpin needs to be connected to the next hairpin bywelding, soldering or the like, and needs to be bent according to aspecific shape in order to make the connection possible. This limits thenumber and size of the conductors that can be fit in a single slot.Another challenge is creating parallel circuits that are balanced andhave reasonably complex connections. Two paths are balanced if theirflux linkage is the same and the voltage is the same.

The electric machine 20 solves these and other problems withoutrequiring jumpers. A jumper is a conductor used to connect hairpins thatare adjacent in the electrical path but are not physically adjacentmaking a direct connect infeasible. A jumper does not extend through theslots and instead extends around the end face or the core. The electricmachine 20 may be a three-phase machine in which the hairpin windings 40are arranged in a U phase, a V phase, and a W phase. Each phase includesassociated hairpins conductors (also known as pins, hairpins, or barconductors) arranged in two or more parallel paths of windings. In theillustrated embodiment, each phase includes two parallel paths. Eachphase may include more or less parallel paths in other embodiments.

The hairpins are generally U-shaped with each bent to include a pair oflegs joined by a crown. The hairpins are installed in the stator core 32by inserting the legs through corresponding ones of the slots 34. All ofthe hairpins may be installed from the same end of the stator core 32,e.g., end 36, so that all of the crowns are located on one end of thestator, e.g., end 36, and the ends of the legs are located on the otherend, e.g., end 38. Once installed, the legs of the hairpins are bent toform twists that connect with the twists of other hairpins. The ends ofcorresponding twists are joined by a connection such as a weld 48. End36 may be referred to as the crown end and end 38 may be referred to asthe weld end (or twist end). The hairpins are typically made of barconductors having a rectangular cross-section, but the hairpins may havea circular or other cross-sectional shape.

The U phase may include a first path 44 and a second path 46. The paths44, 46 are balanced and in parallel. Each path may be equally disposedin the even and odd slots, e.g., path 44 has 24 legs in even slots and24 legs in odd slots. The paths are formed by a plurality ofinterconnected pins 42, that once connected, form a continuous circuit.Each of the paths includes a first end that starts at the U-phaseterminal 50 and a second end that ends to a neutral connection. In theillustrated embodiment, the electric machine 20 includes a singleneutral bar 52, but multiple neutral bars may be used in otherembodiments. The first and second paths 44, 46 connect to the neutralconnection 52 near 53. The paths 44, 46 are connected to each other atthe terminal 50, which is located near the outer diameter (OD) 29 of thestator core. The first and second paths 44, 46 start near the OD. Thefirst and second paths 44, 46 may have five and seven pitch crowngeometry at radially outermost and innermost positions. The selection offive and seven pitch crown geometry are chosen to ensure identicalelectromagnetic slot occupancy between two paths without creating anyphysical hindrance in the crown and twist side geometry. The first andsecond paths 44, 46 may wind (advance), in a zig-zag fashion, in thecounterclockwise direction (when looking at end 38) through the slots 34and end near the OD 29 at the neutral connection 52. The first andsecond paths 44, 46 may be zig-zagged resulting in the paths onlyencircling the stator core once. This is in contrast to most hairpinmotors in which multiple stator revolutions are required to traversefrom the ID to the OD. In the illustrated embodiment, each of the pathsincludes twenty-four pins that are interconnected end-to-end to form acontinuous conductor between the terminal 50 and the neutral connection52 without the need of jumpers.

The V phase may include a first path 56 and a second path 58. The paths56, 58 are balanced and in parallel. The paths are formed by a pluralityof interconnected pins 64. Each of the paths includes a first end thatstarts at the V-phase terminal 66 and a second end that ends at theneutral connection 52 near 55. (In other embodiment, the U and V phasesmay have separate neutral bars.) The paths 56, 58 are connected to eachother at the terminal 66, which is located near the OD 29 of the statorcore. The first and second paths 56, 58 start near the OD 29 of thestator core to connect to the terminal 66. The first and second paths56, 58 may have five and seven pitch crown geometry at radiallyoutermost and innermost positions. The selection of five and seven pitchcrown geometry are chosen to ensure identical electromagnetic slotoccupancy between two paths without creating any physical hindrance inthe crown and twist side geometry. The first and second paths 56, 58wind, in a zig-zag fashion, in the counterclockwise direction throughthe slots 34 and end near the OD 29 at the neutral connection 52. Thefirst and second paths 56, 58 may wind around the stator core only onetime, like the U-phase. In the illustrated embodiment, each of the paths56, 58 includes twenty-four pins that are interconnected end-to-end toform a continuous conductor between the terminal 66 and the neutralconnection 52 without the need of jumpers.

The W phase may include a first path 70 and a second path 72. The paths70, 72 are balanced and in parallel. The paths are formed by a pluralityof interconnected pins 78. Each of the paths includes a first end thatstarts at the W-phase terminal 80 and a second end that ends at theneutral connection 52 near 57 or have a dedicated neutral. The paths 70,72 are connected to each other at the terminal 80, which is located nearthe OD 29 of the stator core. In other embodiments, the U, V, or W phaseterminals may be located near the ID 28. The first and second paths 70,72 start near the OD 29 of the stator core. The first and second paths70, 72 wind in the counterclockwise direction through the slots 34 andend near the OD 29 at the neutral connection 52. Thus, all of the pathsof all of the phase advance in the same direction. The first and secondpaths 70, 72 may have five and seven pitch crown geometry at radiallyoutermost and innermost positions. The selection of five and seven pitchcrown geometry are chosen to ensure identical electromagnetic slotoccupancy between two paths without creating any physical hindrance inthe crown and twist side geometry. The first and second paths 70, 72 maywind around the stator core, in a zig-zag fashion, only one time. In theillustrated embodiment, each of the paths includes twenty-four pins thatare interconnected end-to-end to form a continuous conductor between theterminal 80 and the neutral connection 52. The terminals 50, 66, and 80may include additional leads to connect to the inverter and receivevoltage from the inverter, which creates torque-producing current in thewinding paths causing the rotor 24 to rotate within the stator 22.

The hairpins of each of the paths may include one or more types ofhairpin. Different types of hairpins may differ in shape and/or size.The hairpins of machine 20 may include two main types: hairpins withboth twists extending inward (e.g., FIG. 4A, 4B, 4E) and pins with onetwist extending outward and one twist extending inward (e.g., FIGS. 4Cand 4D).

Referring to FIG. 4A, an example first interior pin 90 may include afirst leg 98 joined to a second leg 100 at a vertex 102. (The pins arenot to scale and the legs are shortened for illustrative purposes.) Thevertex 102 may radially offset the legs to place the legs in differentslot positions. The vertex 102 may be formed by a twist that radiallyoffsets the legs by the dimension of one pin in the radial direction.The pins 90 may be formed from a single piece of metal such as copper,aluminum, silver, or any other electrically conductive material. Thefirst leg 98 is disposed in one of the slots 34 and the second leg 100is disposed in another of the slots 34 that is spaced apart by a span ofslots. The pins 90 may have a span equal to the number of slots perpole, which is six slots in the illustrated embodiment. Thus, if thefirst leg 98 was in Slot 1, the second leg 100 would be in Slot 7. Theleg 98 includes a straight portion 99 disposed within a slot 34 and afirst angled portion 104 that extends between the vertex 102 and thestraight portion 99. The straight portion 99 and the angled portion 104are joined at a first bend 106. The leg 98 also includes a twist 110that is angled inward at a second bend 108. The second leg 100 includesa straight portion 101 disposed within a slot 34 and a first angledportion 112 that extends between the vertex 102 and the straight portion101. The first and second angled portions 104, 112 and the vertex 102maybe collectively referred to as a crown. The straight portion 101 andthe angled portion 112 are joined at a first bend 114. The second leg100 also includes a twist 120 that is angled inward at a second bend118. The twists 110, 120 angle towards each other enabling the windingto zig-zag. The twist 110 and the twist 120 may have the same lengths ofthree slots. Since the both twist 110, 120 fold back over the pin 90,rather than extending away like most hairpins, the pins 90 have arelative short overall span of 6 slots. The pin 90 may be fabricated byfirst forming the vertex 102, the first angled portions 104, 112, andtwo extended straight portions. Then, the pin 90 is installed into thestator 22 by inserting the extended straight portions into the slots 34of the stator 22. The second bends 108, 118 and the twists 110, 120 areformed after the pin 90 is installed through the slots by bending theextended legs as desired. The pins 90 may be used in radial positions 2and 3 as will be described below.

Referring to FIG. 4B, an example second interior pin 92 may include afirst leg 122 joined to a second leg 124 at a vertex 126. The vertex 126may radially offset the legs to place the legs in different slotpositions. The vertex 126 may be formed by a twist that radially offsetsthe legs by the dimension of one pin in the radial direction. The pins92 may be formed from a single piece of metal such as copper, aluminum,silver, or any other electrically conductive material. The twist 128 andthe twist 130 may have the same lengths of three slots. The pin 92 issimilar to pin 90 except that the disposed in radial positions 6 and 7and the bend geometries may differ slightly.

Referring to FIG. 4C, an example first exterior hairpin 94 may include afirst leg 132 joined to a second leg 134 at a vertex 136. (This pin maybe called a connector or a joinder pin depending upon its placement inthe winding.) The vertex 136 may be bent so that each of the legs are ina same slot position. The pins 94 may be formed from a single piece ofmetal such as copper, aluminum, silver, or any other electricallyconductive material. The first leg 132 is disposed in one of the slots34 and the second leg 134 is disposed in another of the slots 34 that isspaced apart by a span of slots. The pins 94 has a span of seven slotsin the illustrated embodiment. The leg 132 includes a twist 136 that isangled inward, and the first leg 134 includes a twist 138 that is angledoutward. That is, the twists 136, 138 extend in the same direction. Thetwist 136, 138 may have the same span, e.g., three slots. The pins 94may have an overall span of 10 slot. The pins 94 may be used nearest theOD 29 or the nearest the ID 28, e.g., positions 1 or 8, depending uponwhich path it is part of.

Referring to FIG. 4D, an example second exterior pin 96 may include afirst leg 140 joined to a second leg 142 at a vertex 148. (This pin maybe called a connector or a joinder pin depending upon its placement inthe winding.) The vertex 148 may be bent so that each of the legs are ina same slot position. The pins 94 may be formed from a single piece ofmetal such as copper, aluminum, silver, or any other electricallyconductive material. The first leg 140 is disposed in one of the slots34 and the second leg 142 is disposed in another of the slots 34 that isspaced apart by a span of slots. The pins 94 may has a span five slotsin the illustrated embodiment. The leg 140 includes a twist 144 that isangled inward, and the second leg 142 includes a twist 146 that isangled outward. That is, the twists 144, 146 extend in the samedirection. The twist 144, 146 may have the same span, e.g., three slots.The pins 96 may have an overall span of eight slots. The pins 96 may beused nearest the OD 29 or the nearest the ID 28 depending upon whichpath it is part of.

Referring to FIG. 4E, an example third interior pin 97 may include afirst leg 105 joined to a second leg 107 at a vertex 109. The vertex 109may radially offset the legs to place the legs in different slotpositions. The legs are spaced part by either five or seven slots (shownas seven). The vertex 109 may be formed by a twist that radially offsetsthe legs by the dimension of one pin in the radial direction. The pins97 may be formed from a single piece of metal such as copper, aluminum,silver, or any other electrically conductive material. The twist 111 andthe twist 113 both extend inwardly may have the same lengths of threeslots. Unlike the pins 90 and 92, the ends 115 and 117 are not locatedat the same slot and instead are offset by one slot. This results ineither the gap 119 in the seven-slot embodiment, or a crisscross in thefive-slot embodiment. The pin 97 is disposed in a middle position, e.g.,radial positions 4 and 5.

Referring to FIGS. 2 and 5, the slots 34 are numbered 1 through 48 inthe counterclockwise direction with the odd number slots being labeledfor convenience. The slots 34 may include positions in the radialdirection, which may be referred to as radial slot positions, radialpositions, slot positions, or positions. Each position represents apin-receiving area that receives one leg of a hairpin. In theillustrated embodiment, each slot 34 has eight sequential positions in aone-by-eight linear arrangement, however, other arrangements arecontemplated. Thus, in the illustrated embodiment, each slot 34 includeseight legs, one in each slot position. The positions are labeled 1through 8, with the first position being nearest the ID and the eighthposition being nearest the OD. Positions 1 and 8 may be referred to asexterior positions and positions 2-7 may be referred to as interior (orintermediate) positions. The intermediate positions may include innerintermediate positions, e.g., positions 2 and 3, and outer intermediatepositions, e.g., positions 6 and 7. The term “radial slot position” isused to describe both a single position of a single slot and to refer tothe collective positions at that radial location of the stator core 32.(The slot positions are sometimes referred to as radial layers as theslot positions are aligned and collectively form concentric rings aroundthe stator core. It is important to note that these radial layers referto something different than the above-described single and double-layerwinding arrangements, which refer to the number of phases in each slot.)

Referring to FIG. 5, the illustrated winding 40 is a double-layerwinding. In slot 1, only the U phase is contained therein, but, slot 2contains both the U phase and the W phase. Other slots may only containthe V phase, only contain the W phase, contain the U and V phases, orcontain the V and W phases. The shift for single to double phase mayoccur at the midpoint of the slots, e.g., slot only includes the samephase in positions 5-8 and may include a different phase in positions1-4, or vice versa.

Referring to FIG. 6, a winding diagram of the U phase is shown. In themachine 20, the paths may be wound in a repeating pattern of blocks 150.Each of the blocks may be the same, albeit shifted circumferential todifferent slots. In a 48-slot stator, the windings include four blockseach containing 12 consecutive slots. In this description, the blocks150 will be delineated at position 8, however, this is arbitrary. Eachblock 150 begins at the trailing end of the first hairpin and terminatesat the leading end of the last hairpin. The terms “leading” and“trailing” refer to the position of the component relative to thedirection of advancement through the path with the terminal beingconsidered the start and the neutral being the end. Each block mayinclude eight hairpins: one hairpin 96, which is the first hairpin inpath 44, one hairpin 94, which is the fifth hairpin in path 44, twohairpins 90 (in positions 2 and 3), two hairpins 92 (in positions 6 and7), and two hairpins 97 (in positions 4 and 5).

Unique to this arrangement is that each path 44, 46 of windingstraverses from the OD to the ID and back to the OD within each block150, e.g., within a span of 12 slots. Most winding arrangements arewound circumferentially and require one or more revolutions of thestator to traverse from the OD to the ID and back. This windingarrangement employees a zig-zag route to achieve a large amount ofradial displacement is a short amount of circumferential advancement.The zig-zag is created mostly by the interior pins 90, 92, and 97, whichhave both twists extending inwardly. Each block 150 may include a pairof sub-blocks 152, 154. A sub-block refers to a collection of hairpinsthat traverse in one radial direction, i.e., from the OD to the ID(sub-block 152) or form the ID to the OD (sub-block 154). In the firstpath 44, the hairpins 94 interconnect the sub-blocks 152 and 154 and thehairpins 96 are used to interconnect adjacent blocks 150.

Referring to FIG. 7, the first block 150 a of the first path 44 beginsat slot 40 with the first hairpin 156, which is an exterior pin 96. Anend of the twist 146 is located above slot 40 and is joined by a weld160 to the last hairpin of the fourth block, which is a hairpin 92. Thetrailing leg 142 of the hairpin 156 is disposed in slot 37 and theleading leg 140 is disposed in slot 32. Both legs are disposed in theeighth position. The crown 148 of the hairpin 156 advances the path 44forward five slots. The twist 144 of the leading leg 140 then retardsthe path 44 back three slots. The twist 128 of the second hairpin 158further retards the path by three more slots to place the trailing leg122 in the seventh position of slot 38 and the leading leg 124 in thesixth position of slot 32. The twist 128 is joined to the first hairpin156 by a weld 160. The crown 126 of the hairpin 158 advances the path 44forward six slots and the twist 130 then retards the path 44 back threeslots. The third hairpin 162 is of the type 97. The third hairpin 162includes a trailing leg 105 disposed in the fifth position of slot 38and a leading leg 107 disposed in the fourth position of slot 31. Thelegs 105 and 107 are spaced apart by seven slots and the twist are boththree slots. Thus, the hairpin 162 advances the path 44 forward by oneslot to create the double layer windings. In other embodiment, thehairpin 162 may have a span of five slots between the legs. This wouldretard the path 44 backward by one slot while still creating doublelayer windings. The fourth hairpin 164 is of the type 90. The fourthhairpin 164 includes a trailing leg 122 disposed in the sixth positionof slot 37 and a leading leg 124 disposed in the seventh position ofslot 31.

The fifth pin 166, which is a joinder pin and of the type 94, isconnected between the fourth pin 164 (last pin of sub-block 152) and thesixth pin 168 (first pin of sub-block 154). The trailing twist 138 isconnected to the hairpin 164 and retards the path 44 by three slotswhereas the leading twist 136 advances the path 44 by three slots. Thetrailing leg 134 of the pin 166 is disposed in the first position ofslot 37 and the leading leg 132 is disposed in the first position ofslot 30. The leading twist 136 advances forward by three slots toconnect to the sixth pin 168. The sixth pin 168, which is an interiorpin 90, includes a trailing leg 100 disposed in the second position ofslot 24 and a leading leg 98 disposed in the third position of slot 30.In contrast to the sub-block 152, the hairpins of the sub-block 154 areadvanced by the twists and are retarded by the crowns. The seventh pin170, which is a pin 97, includes a trailing leg 107 disposed in thefourth position of slot 24 and a leading leg 105 disposed in the fifthposition of slot 31. The trailing twist 113 of the seventh pin 170 isjoined to the leading twist 110 of the sixth pin 168. The leading twist111 is connected to next interior pin 92, eight pin 172. The eighth pin172 has a trailing leg 124 disposed in sixth position of slot 25 and aleading leg 122 disposed in the seventh position of slot 31. The leadingtwist 128 is connected to the connector pin of the next block 150. Thispattern repeats itself around the stator core 32.

The first block 150 a of the second path 46 begins at slot 41 with thefirst hairpin 174, which is an exterior pin 94. An end of the twist 136is located above slot 41 and is welded to the last hairpin of the fourthblock. The second path 46 is similar to path 44 except the second pathincludes the pins 94 in position 8 and the pins 96 in position 1. Likepath 44, the path 46 also includes pins 97 in the middle slot position,e.g., positions 4 and 5.

Referring back to FIG. 6, in the illustrated embodiment, the twists ineach radial position extend from their respective leg in a samecircumferential direction and have a same slot span. For example,hairpins that have legs in the first position have associated twiststhat extend clockwise; hairpins that have legs in the second positionhave associated twists that extend counterclockwise; hairpins that havelegs in the third position have associated twists that extend clockwise,etc. This in combination with the other above-described features placesthe to-be-connected twists adjacent to each other so that they can bedirectly joined without the need for any jumpers. This may be true forthe other phases as well.

Referring to FIGS. 8 and 9, the V and W phases of the windings 40 may bethe same as the U phase but shifted to different slots. The V phase maybe shifted over four slots in the counterclockwise direction to have thefirst pin of path 56 disposed in slot 5 and 48 and to have the first pinof path 58 disposed in slots 6 and 47. The W phase may be shifted overeight slots from the U phase in the counterclockwise direction to havethe first pin of path 70 disposed in slot 9 and 4 and to have the firstpin of path 72 disposed in slots 10 and 3. Please see the windingdiagrams for the remain hairpin locations.

This disclosure is not limited to the above-described windingarrangements and contemplates any winding having ID and OD hairpins withslot spans of five and seven, respectfully or vice versa, and middlehairpins that have a span of one more, e.g., five or seven, than theother intermediate hairpins, e.g., span of six slots.

While exemplary embodiments are described above, it is not intended thatthese embodiments describe all possible forms encompassed by the claims.The words used in the specification are words of description rather thanlimitation, and it is understood that various changes can be madewithout departing from the spirit and scope of the disclosure. Aspreviously described, the features of various embodiments can becombined to form further embodiments of the invention that may not beexplicitly described or illustrated. While various embodiments couldhave been described as providing advantages or being preferred overother embodiments or prior art implementations with respect to one ormore desired characteristics, those of ordinary skill in the artrecognize that one or more features or characteristics can becompromised to achieve desired overall system attributes, which dependon the specific application and implementation. These attributes caninclude, but are not limited to cost, strength, durability, life cyclecost, marketability, appearance, packaging, size, serviceability,weight, manufacturability, ease of assembly, etc. As such, embodimentsdescribed as less desirable than other embodiments or prior artimplementations with respect to one or more characteristics are notoutside the scope of the disclosure and can be desirable for particularapplications.

What is claimed is:
 1. An electric machine comprising: a stator coredefining slots having a plurality of radial positions including an innerposition, an outer position, and a pair of middle positions; and adouble-layer winding disposed in the core and having first and secondparallel paths each including hairpins directly interconnected to eachother to form a continuous circuit between a terminal and a neutralwithout using jumpers, wherein each of the hairpins includes a first legdisposed in one of the slots, a second leg disposed in another of theslots, a crown connecting between the legs, and at least one inwardlyextending twist joined to one of the legs, and wherein, for each of thepaths, a first subset of the hairpins (first hairpins) have their firstand second legs disposed in the inner position, and a second subset ofthe hairpins (second hairpins) have their first and second legs disposedin the outer position.
 2. The electric machine of claim 1, wherein, foreach of the paths, a third subset of the hairpins (third hairpins) havetheir first leg disposed in one of the middle positions and their secondleg disposed in the other of the middle positions.
 3. The electricmachine of claim 2, wherein, for each of the paths, the first and secondhairpins have different slot spans than each other, and the thirdhairpins have a same slot span as one of the first and second hairpins.4. The electric machine of claim 3, wherein the first hairpins have aslot span of seven and the second hairpins have a slot span of five. 5.The electric machine of claim 4, wherein the third hairpins have a slotspan of seven.
 6. The electric machine of claim 4, wherein the thirdhairpins have a slot span of five.
 7. The electric machine of claim 3,wherein the first hairpins have a slot span of five and the secondhairpins have a slot span of seven.
 8. The electric machine of claim 2,wherein the plurality of radial positions further includes a pair ofouter intermediate positions between the outer position and the middlepositions, and wherein, for each of the paths, a fourth subset of thehairpins (fourth hairpins) have their first leg disposed in one of theintermediate positions and their second leg disposed in the other of theintermediate positions.
 9. The electric machine of claim 8, wherein, foreach of the paths, the first and second hairpins have different slotspans than each other, the third hairpins have a same slot span as oneof the first and second hairpins, and the fourth hairpins have a slotspan that is different than the first hairpins and the second hairpins.10. The electric machine of claim 9, wherein the first hairpins have aslot span of five, the second hairpins have a slot span of seven, thethird hairpins have a slot span of seven, and the fourth hairpins have aslot span of six.
 11. The electric machine of claim 1, wherein, for eachof the paths, a third subset of the hairpins (third hairpins) eachfurther includes another inwardly extending twist extending from theother of the legs.
 12. The electric machine of claim 1, wherein thewinding includes three phases each having the first and second paths.13. The electric machine of claim 1, wherein the stator core defines 48slots.
 14. An electric machine comprising: a stator core defining slotshaving a plurality of radial positions; and a winding disposed in thecore and having three phases, each of the phases having at least twoparallel paths including hairpins interconnected to form at least twocontinuous circuits between a terminal and a neutral, wherein thehairpins of each path include: a first type of hairpins (first hairpins)each having first and second legs spaced apart by a span of five slots,wherein each of the first hairpins has an inwardly extending twistjoined to one of the legs and an outwardly extending twist joined to theother of the legs, a second type of hairpins (second hairpins) eachhaving first and second legs spaced apart by a span of seven slots,wherein each of the second hairpins has an inwardly extending twistjoined to one of the legs and an outwardly extending twist joined to theother of the legs, and a third type of hairpins (first hairpins) eachhaving first and second legs spaced apart by a span of five or sevenslots, wherein each of the third hairpins has a first inwardly extendingtwist joined to one of the legs and a second inwardly extending twistjoined to the other of the legs; wherein the legs of the first hairpinsare disposed in a first one of the positions, and the legs of the secondhairpins are disposed in a second one of the positions.
 15. The electricmachine of claim 14, wherein the hairpins of each path further include afourth type of hairpins (fourth hairpins) each having first and secondlegs spaced apart by a span of six slots.
 16. The electric machine ofclaim 14, wherein the third type of hairpins has a span of five slots.17. The electric machine of claim 14, wherein the third type of hairpinshas a span of seven slots.
 18. The electric machine of claim 14, whereinat least one of the slots only has one of the phases disposed therein,and at least one of the slots has two of the phases disposed therein.19. An electric machine comprising: a stator core defining slots havinga plurality of radial positions; and jumperless windings disposed in thecore and arranged in three phases each having at least two pathsincluding hairpins interconnected to form at least two continuouscircuits between a terminal and a neutral, wherein the hairpins of eachpath include: a first type of hairpins (first hairpins) each having afirst leg, a second leg, a crown connecting between the legs, anoutwardly extending twist joined to the first leg, and an inwardlyextending twist joined to the second leg, wherein the legs are spacedapart by a span of five slots and are located in a same first one of theradial positions, a second type of hairpins (second hairpins) eachhaving a first leg, a second leg, a crown connecting between the legs,an inwardly extending twist joined to the first leg, and an outwardlyextending twist joined to the second leg, wherein the legs are spacedapart by a span of seven slots and are located in a same second one ofthe radial positions, and a third type of hairpins (third hairpins) eachhaving a first leg disposed in a third one of the radial positions, asecond leg disposed in a fourth one of the radial positions, a crownconnecting between the legs, a first inwardly extending twist joined tothe first leg, and a second inwardly extending twist joined to thesecond leg, wherein the legs are spaced apart by a span of five or sevenslots; wherein at least one of the slots only has one of the phasesdisposed therein, and at least one of the slots has two of the phasesdisposed therein.